1. Field of the Invention
The present invention relates to a pixel structure of a display and, more particularly, to a pixel structure having a metal-insulation-metal (MIM) transistor to provide a blanking effect.
2. Description of the Related Art
The manufacture and use of thin film transistor liquid crystal display (TFT-LCD) is well known in the art. FIG. 1 is an equivalent circuit diagram of a conventional TFT-LCD. On an LCD panel 1, data electrodes in a sequence of D1, D2, D3 and Dy and scanning electrodes in a sequence of G1, G2 and Gx are arranged in a crisscross pattern to control display cells arranged in a matrix form. For example, the data electrode D1 and the scanning electrode G1 are employed to control the display cell 100. The display cell 100, the same as other display cells, comprises a thin film transistor 101, a storage capacitor 103 and an LCD capacitor 102, in which the LCD capacitor 102 comprises a display electrode and a common electrode. The thin film transistor 101 has a gate electrode electrically connected to the scanning electrode G1, and a drain electrode electrically connected to the data electrode D1, wherein scanning signals on the scanning electrode G1 control the on/off state of the thin film transistor 101 to write video signals on the data electrode D1 into the display cell 100. Also, according to scanning control data, a scanning driver 3 delivers scanning signals on the scanning electrodes in a sequence of G1, G2 and Gx to simultaneously turn on thin film transistors arranged on only one row of display cells and turn off other thin film transistors arranged on other (x−1) rows of display cells. When the thin film transistors arranged on one row of display cells are turned off, a data driver 2 delivers video signals (gray scale) corresponding to predetermined image data to y display cells arranged on the same row through the data electrodes in a sequence of D1, D2, D3 and Dy. After the scanning driver 3 scans x rows of gate electrodes once, a single frame of display is completed. Thereafter, by repeated scanning of the scanning electrodes to deliver video signals, predetermined images are displayed.
The same scanning method is also applied to an organic light emitting diode (OLED) in which circuit structure is similar to that of the TFT-LCD. FIG. 2 is an equivalent circuit diagram of a conventional OLED. On an OLED panel 11, data electrodes in a sequence of D1, D2, D3 and Dy and scanning electrodes in a sequence of G1, G2 and Gx are arranged in a crisscross pattern to control display cells arranged in a matrix form. For example, the data electrode D1 and the scanning electrode G1 are employed to control the display cell 200. The display cell 200, the same as other display cells, comprises two thin film transistors 201 and 202, an OLED unit 203 and a storage capacitor 204. The thin film transistor 201 has a gate electrode electrically connected to the scanning electrode G1, and a drain electrode electrically connected to the data electrode D1, wherein scanning signals on the scanning electrode G1 control the on/off state of the thin film transistor 201 to write video signals on the data electrode D1 into the display cell 200. Also, according to scanning control data, a scan driver 13 delivers scanning signals on the scanning electrodes in a sequence of G1, G2 and Gx in sequence to simultaneously turn on the thin film transistors arranged on only one row of display cells and turn off other thin film transistors arranged on other (x−1) rows of display cells. When the thin film transistors arranged on one row of display cells are turned on, a data driver 12 delivers video signals (gray scale) corresponding to predetermined image data to y display cells arranged on the same row through the data electrodes in a sequence of D1, D2, D3 and Dy. After the scanning driver 13 scans x rows of scanning electrodes once, a single frame of display is completed. Therefore, by repeated scanning of the scanning electrodes to deliver video signals, predetermined images are displayed.
FIG. 3 shows a function of illumination and time according to the above-described display cells, in which the illumination is based on the condition of the LCD capacitor 102 or the OLED unit 203. As well known in the art, the image retention characteristic of the human eye allows successive frames from the display cell to be seen. This characteristic is similar to image integration from the human eye, and a function of illumination and time with regards to the human eye is shown in FIG. 4 in which moving images look vague.
In order to solve the above-described problem, one current approach is to blank the illumination in predetermined portions as shown by oblique lines in FIG. 5, resulting in the desired interaction between illumination and time (as shown in FIG. 3) acting on the human eye. However, this only adjusts brightness towards vision without solving the above-described problem generated in darkness towards vision.
Also, control of the blanking time is very important. If the blanking time is too short, vague images are still generated. If the blanking time is too long, the illumination of the display cell darkens to decrease display performance. However, the blanking time is commonly fixed within a specific time of the display period, and is therefore unable to immediately adjust the blanking time in accordance with the practical signal status. In order to properly control the blanking time, another current approach is to add extra driving devices or change scanning frequency. Circuit components are consumed to modify the circuit structure.